Frothing agents for flotation of ores



Patented Sept. 23, 1952 y UNITED STATE Elmer -Walnut Creek, Calif; assignor to ThaaDow; Chemical" Company, Midland, Michaacorporation oLDelawarc- NoDr-awing. Application April 21, 1949,

Serial No. 88,891

1 The invention relates to new and improved frothlng: agents for use in processes for the froth ffiotation'of ores.

Although a multiplicity of compounds has been disclosedin the art,'which are said to be effec- 5 Claims. (01. 209-166) tive frothing agents, few of them have been adopted in commercial practice for reason-s of cost, availability and performance. For practical reasons pine oil and cresylic acid havebeen most widely used and are generally. regardedby I the art as the standard frothing. agentsi I have now found that the lower alkyl. and

phenyl mono-ethers' of propylene glycol and of the poly-propylene glycols are highly effective frothing agents and that for many ores they'show a marked superiority as compared with the standard frothers. These compounds are now avail- "able: in good supply-eta cost which. permits their use in large scale ore-dressing operations.

' Compounds which have been. found useful as f rothers. according to the invention are the methy1-,-=eth-yl-, propyl-; butyl-,. and phenyl-monoethers of propylene 'glycolrand of: d-i-,. tri-, tetra-, and higher, propylene glycols, as well as mixtures thereof. Instead of using the purified compounds for the purpose. reaction mixtures. obtained by usual methods of making the compounds, or

mixed fractions thereof, may alsobe used.

The aforesaid mono-ethers of propylene-glycol and. poly-propylene glycols may be made according to any of the methods known 'toth'e art; They are prepared by the reaction ofa'n alcohol or phenol with propylene oxide according to' the equation ROH+7LCrHeO- R- ('OCrLHsM-OH where R represents a hydrocarbon radical and n .is' the number of mols of propylene oxide used.

The greaterthe value of n, the longer isthe average chain length of the mono 'ether produced. For carrying out the reaction the alcohol or phenol is placed in a closed reactor and a small amount of an alkali metal hydroxide, e. g. NaOH,

is added as catalyst, on the order of about 0.5'to

gauge. The reaction product is neutralized with .acid, and may be distilled to remove more volatile components, leaving the glycol or polyglycol I ether as a high boilin residue.

The mono-ethers of propylene glycol and poly? propylene glycols are effective producers of a strong froth possessing the physical properties. required for supporting the mineral particles and permitting a clean separation from the gangue.

As compared with the standard frother-s, pine oil and cresylic acid, the new agents are. capable of producingan equivalent froth with a materially smaller quantity of the frothing agent, hence are markedly superior in specific frothing power; In the casefof manyores they show greaterxselec+ tlvity; producing a richer concentratew=with .=a lowercontent of" acid-insolubleganguematerial's. The propylene'glycol and poly-propylene glycol mcno-ethers are not efiective as mineral colleetors, their function in the flotation process being solely that of frothi'ng agent. The art has long recognized that it is disadvantageous for frothing agents to possess good collecting prop- .ertiesgas better selectivity is found when the two functions are separately performed by appropriate agents. 1 W I I The followingexamples illustrate .the improved results obtainable by use of the invention.

I a EXAMPLE' I 1 I .A: series of. tests was made with asulphidelcopper or assaying 4.03. per. cent Cu. 6010 gram samples of the ore were ground in a ball mill with 300 ml. of water and with lime inproportion of 5.0 pounds per ton. of ore to prepare a pulp .in which. 56 per cent or the solids passed a 200 mesh screen. The pulp was conditioned ina. flotation. cell, with potassium pentasol xan'thate in amount of 0.025 pound .per ton. of ore, and. with the ramount of frothing agent shownin the following table, after which the concentrate was removed in 6 minutes of frothing. Table I shows the analysis of thelconcentrate. and percentage recovery of. copper. In one test pine oil wasused as the frother for comparison,

:Table I v 'C oncentrate Frother Pine oil Tripropylene glycol phenyl ethen. Propylene glycol n-butyl ether"- Tripropylcne glycol n-butyl ether The amounts of frother used in the tstswre The ref;

same volume of froth.

show 50 per cent greater amount of pine oil rethose required to produce approximately l the The tabulated results quired than of the various propylene 'g lycol 'ethers- Greater selectivity of the latter is also shown in the lower content of acid-insoluble materialin theconcentrate.

EXAMPLE 2 3 65 per eeiltbf. solids passinga 200: mesh screen. The pulp was'conditioned for one minute with utes of frothing.

amount of frother used in all cases beingfthat- .1

required to produce approximately the same-vol ume of froth. The results are shown in Table II:

Table II Concentrate L IT Pecent OD u From oi Ore Cu Insol. Recov- .Perl-"er-v ery cent cent Pine on 0507 1 1. 4 1 3311 78.6 Crcsylic acid 0. 13 ll. 6 36. 6 79. 3 Propylene glycol phenyl ether 0.08 I 12.3 29. 9 '78. O Dipropylene glycol phenyl ether. 0. 08 11.5 33. 7 80.2 Propylene glycol n-butyl ether." 11.4 35. 5 81. 4 Dipropylene glycol n-butyl ether. 0.05 11. 1 33.1 84:2 Tetrapropylene glycol n-butyl ether 0.05 -10.6 36.7 81.8 Pentapropylene glycol n-butyl ether 0. 05 11. 0 35. 2 80.6

In this series of tests a lead-zinc sulphide ore, which assayed 3.8 percent Pb and 5.8 per cent Zn, was floated in two stages to remove, first, a lead concentrate andthen a zinc concentrate. The ore was crushedto pass a 10-mesh screen. Samples of 500 grams of the crushed ore were ground in a .ball mill with 300 ml. of Water, lime at the rate of 0.8 pound per ton of ore, zinc sulfate at the rate of 0.44 pound per ton, sodium cyanide at the rate of 0.16 pound per ton, and

potassium ethyl xanthate at' the rate of 0.03 pound per ton, to a pulp in which 70 per cent of the solids passed a ZOO-mesh screen. The pulp was conditionedfor one minute with the frother as shown in the table and a lead concentrate was removed during 4 minutes of frothing. The pulp table for the zinc concentrate. The zinc concentrate was removed during 6 minutes of frothing. 1

In each case the volume of froth was approxi- -mately the same for each of the frothers tested.

The results are shown in Table III, the test including both cresylic acid and pine oil for com- Samples of the copper on: described in Examp1e 1 were prepared and ground in similar man- ;iier, usin lime at 7.0 pounds per ton and as q collector a mixture of equal parts of sodium ethy1 xanthate and potassium amyl xanthate at 0.04 pound per ton.. The propylene glycol ether 'frothing agents used were in each case obtained from two different sources and were tested against 1: pine oilfor comparison, in the amounts shown -I in the table. The concentrates were removed in 6 minutes of frothing, the results being given in Table IV:

Samples (0) and (b) obtained from separate sources.

v EXAMPLE 5 In this series of tests the same copper ore was used as in Examples 1 and 4, which was prepared as in Example 4. As frothing agents mixed reaction products were used, asfollows: Y

PPG methyl ether.--A mixture of poly-propylene glycol methyl ethers. principally the ether of tetrapropyle'ne glycol, obtained as the still residue from the reaction product of propylene oxide and methanol, after distilling off the lower ethers.

PPG isopropyl ether (1) .The undistilled reaction producttrom 1.67 mols of propylene oxide and one mol of isopropanol, containing approximately 21.0 per cent of isopropanol, 19.0 per cent of propylene glycol isopropyl ether, and the balance a mixture of poly-propylene glycol isopropylethers.

PPG isopropyl ether (2).The undistilled reaction product from 4 mols of propylene oxide and one mol of isopropanol, containing about 8.0 per cent of isopropanol, 7.0 per cent of propylene glycol isopropyl ether, and the balance a -parison.- mixture Qf p yp pylene gly ol isopropyl ethers.

Table III V Assay iPercent Distribution I Type Frother g 'gg Product Pb Zn Insole Percent Pegcent Cresylic acid 0. 0s Pb Cone" 43.3 13.4 1412 91.4 18.0 3 Do 0.16 Zn Conc 1.7 38.6 21.9 5.0 76.8

Total.. 024 Tailingi... 0.18 0. 32 3.6 4. a I 0.05 Pb Conc 42.9 12.8 16.6 90.6 18.2 0. 13 Zn Gone" 1. 9, 41. 6 20. 6 5. 3 79. 7

Total -Q Telling... 0.20 0.16 4.1 2.1

Tripropylene glycol mono-n-butyl ether- 0.08 Pb Conc 40. 6 15. 2 14. 4 91. 0 23. 1 Do 0. 07 Zn Conc l. 8 40. 5 18. 7 5.0 74. 4

Total 0.10 Tailingun 0. 20 0.18 4. 0 2. 5

Dipropylenc glycol phenylether 0. 05 Pb Cone" 46. 0 I ll. 0 15. 3 89. 4 l5. 4 v Do.- 0.10 Zn Conc. 2.3 "41.4 17.5 6.8 82.7

0.15 Tellin 0.10 0.14 3.8 1.9

These frothing agents were tested against pine oi1 as standard, in the amounts and with the results shown in Table V:

Table V Concentrate lgenfint u e- Frother Lb./Ion Cu Insol Per- Perery cent cent PPG methyl ether 0.057 21.8 13.8 92.8 PPGisopropyl ether (1) 0.050 23.2 13.1 92.2 PPGisopropyl ether (2 0.056 22.6 14.3 92.0 Plne oil 0.068 21.4 16.3 92.2

I claim: 1. In the concentration of ores by froth flotation, the method which comprises subjecting an aqueous pulp of the ore to froth flotation in the presence of a collector and of a frother composed essentially of a compound from the group consisting of the alkyl mono-ethers, having from one to four carbon atoms in the alkyl group, and phenyl monoethers of propylene glycol, the polypropylene glycols and mixtures thereof.

2. Method according to claim 1, in which the frothing agent consists essentially of methyl mono-ethers of propylene glycol and the polypropylene glycols.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,730,061 Davidson Oct. 1, 1929 1,970,578 Schoeller Aug. 21, 1934 2,228,929 Von Reibnitz Jan. 14, 1941 OTHER REFERENCES Journal of Physical Chemistry, vol. XIQKVI, January 1932, pages 132 to 137. 

1. IN THE CONCENTRATION OF ORES BY FROTH FLOTATION, THE METHOD WHICH COMPRISES SUBJECTING AN AQUEOUS PULP OF THE ORE TO FROTH FLOTATION IN THE PRESENCE OF A COLLECTOR AND OF A FROTHER COMPOSED ESSENTIALLY OF A COMPOUND FROM THE GROUP CONSISTING OF THE ALKYL MONO-ETHERS, HAVING FROM ONE TO FOUR CARBON ATOMS, IN THE ALKYL GROUP, AND PHENYL MONOETHERS OF PROPYLENE GLYCOL, THE POLYPROPYLENE GLYCOLS AND MIXTURES THEREOF. 